Solar power with grid as backup

Cariboocoot wrote: »

Inverter efficiency isn't 77%. If it is, get a different inverter. The 77% derating is average panel output plus MPPT charge controller loss, so 400 Watts rating of panel in comes out as 308 Watts. Inverters are usually around 90% efficient. Some less, some more.

Cariboocoot wrote: »

With a PWM controller you can only count of the current so you need to know the panel specs. A 200 Watt panel with a Vmp of 35 produces 5.7 Amps but a 200 Watt panel with a Vmp of 30 produces 6.6 Amps. And therein lies a caution about Vmp: it has to be high enough to charge the batteries. This goes along these lines: 12 Volt system Vmp 17-18, 24 Volt system Vmp 35-36, 48 Volt system Vmp 70-72. (Although a 48 Volt system may have a slightly lower Vmp as the wiring losses are inevitably less due to the high Voltage.)

Cariboocoot wrote: »

You say four 102 Amp hour batteries in series. 12 Volt? That would be a 48 Volt system. Hence the caution about array Vmp. It would also supply roughly 1kW hour AC at 25% DOD so that is also good. The only possible issue is the panel Vmp and making sure the charge controller can handle 48 Volts (many PWM types can not).

• Do not exceed a battery voltage of 48V nominal (24 cells). Do not use a battery less than 12V (6 cells).
• Do not connect a solar input greater than a nominal 48V array for battery charging. Never exceed a Voc (open-circuit voltage) of 125V.
• Charge only 12, 24, or 48 volt lead-acid batteries when using the standard battery charging programs in the TriStar.

Cariboocoot wrote: »

Okay, no. not going to work. Panels with Vmp of 26.5 in series gives 53 Vmp and that is not high enough to charge a 48 Volt system. That will have an Absorb Voltage around 58-60. The batteries would never charge.

Cariboocoot wrote: »

Whenever you use a PWM type controller you need the Vmp to be in those guidelines I mentioned. As in 70 Vmp for a 48 Volt system. If you put a 3rd one of those panel in series you end up over that @ 79.5 and some of that will be wasted by a PWM controller as it only passes current.

Cariboocoot wrote: »

BTW for your own system you might want to look at the specs of the MidNite Classic. It's more money than an FM80 but it has some interesting extra features which you might find useful, including direct connection to a battery monitor (their WhizBang Jr) and a "Waste Not" function for making best use of available PV power not going to charge at the moment. Exact adaptation for your use may require some thinking and rethinking but it's worth considering.

westbranch wrote: »

What 'glass' are you referring to wrt the Classic?

Cariboocoot wrote: »

Even though Victron is a quality brand I'd suggest you avoid any all-in-one inverter/charger/solar controller. They have a tendency to lack the necessary flexibility for adapting to individual usage. In other words you get stuck with an inadequate charge controller function that can't be adapted to your specific battery needs.

Cariboocoot wrote: »

You'd want to know just how many of the parameters are programmable and to what extent. Too often you can't alter things to suit the batteries you need to use. Be wary.

2.5 Configuration Assistants
Several software programs (Assistants) are available to configure the system for various grid interactive or stand alone applications.

Cariboocoot wrote: »

maximum input Voltage 75 - well that's not great - and current out 50 - also not great. Absorb default Voltage 28.8 which is good, but probably have to read the whole manual to see how adaptable it is. I'm too lazy to do that.

2.3 Battery Charger
Adaptive 4-stage charge characteristic: bulk – absorption – float – storage
The MultiPlus Compact features a microprocessor controlled ‘adaptive’ battery management system that can be preset to suit different Typs of batteries. The ‘adaptive’ feature will automatically optimize the process relative to the way the battery is being used.

The right amount of charge: variable absorption time
When only shallow discharges occur (a yacht connected to shore power for example) the absorption time is kept short in order to prevent overcharging of the battery. After a deep discharge the absorption time is automatically increased to make sure that the battery is completely recharged.

Preventing damage due to excessive gassing: the BatterySafe mode
If, in order to quickly charge a battery, a high charge current in combination with a high absorption voltage has been chosen, the MultiPlus Compact will prevent damage due to excessive gassing by automatically limiting the rate of voltage increase once the gassing voltage has been reached.

Less maintenance and aging when the battery is not in use: the Storage mode
The storage mode kicks in whenever the battery has not been subjected to discharge during 24 hours. In the storage mode float voltage is reduced to 2,2V/cell (13,2V for a 12V battery) to minimize gassing and corrosion of the positive plates. Once a week the voltage is raised back to the absorption level to ‘equalize’ the battery. This feature prevents stratification of the electrolyte and sulphation, a major cause of early battery failure.

To increase battery life: temperature compensation
Every MultiPlus Compact comes with a battery temperature sensor. When connected, charge voltage will automatically decrease with increasing battery temperature. This feature is especially recommended for sealed batteries and/or when important fluctuations of battery temperature are expected.

Preventing damage due to excessive gassing: the BatterySafe mode
If, in order to quickly charge a battery, a high charge current in combination with a high absorption voltage has been chosen, the MultiPlus Compact will prevent damage due to excessive gassing by automatically limiting the rate of voltage increase once the gassing voltage has been reached.

Less maintenance and aging when the battery is not in use: the Storage mode
The storage mode kicks in whenever the battery has not been subjected to discharge during 24 hours. In the storage mode float voltage is reduced to 2,2V/cell (13,2V for a 12V battery) to minimize gassing and corrosion of the positive plates. Once a week the voltage is raised back to the absorption level to ‘equalize’ the battery. This feature prevents stratification of the electrolyte and sulphation, a major cause of early battery failure.

To increase battery life: temperature compensation
Every MultiPlus Compact comes with a battery temperature sensor. When connected, charge voltage will automatically decrease with increasing battery temperature. This feature is especially recommended for sealed batteries and/or when important fluctuations of battery temperature are expected.

PV short circuit and PV reverse polarity protection.
PV reverse current protection.

Internal temperature sensor
Compensates absorption and float charge voltages for temperature.

Adaptive three step charging
The BlueSolar MPPT Charge Controller is configured for a three step charging process:
Bulk – Absorption - Float.

Bulk stage
During this stage the controller delivers as much charge current as possible to rapidly recharge the batteries.

Absorption stage
When the battery voltage reaches the absorption voltage setting, the controller switches to constant voltage mode.
When only shallow discharges occur the absorption time is kept short in order to prevent overcharging of the battery. After a deep discharge the absorption time is automatically increased to make sure that the battery is completely recharged. Additionally, the absorption period is also ended when the charge current decreases to less than 2 A.

Float stage
During this stage, float voltage is applied to the battery to maintain it in a fully charged state.

3.3 Equalisation and forced absorption [\B]

3.3.1 Equalisation
Traction batteries may require regular equalisation charging. In the equalisation mode, the MultiPlus will charge with increased voltage for one hour (1V above the absorption voltage for a 12V battery, 2V for a 24V battery). The charging current is then limited to 1/4 of the set value. The “bulk” and “absorption” LEDs flash intermittently.

3.3.2 Forced absorption
Under certain circumstances, it can be desirable to charge the battery for a fixed time at absorption voltage level. In Forced Absorption mode, the MultiPlus will charge at the normal absorption voltage level during the set maximum absorption time. The “absorption” LED will be ‘on’.

3.3.3 Activating equalisation or forced absorption
The MultiPlus can be put into both these states from the remote panel as well as with the front panel switch, provided that all switches (front, remote and panel) are set to “on” and no switches are set to “charger only”.

Standard MultiPlus factory settings
Inverter frequency 50 Hz
Input frequency range 45 - 65 Hz
Input voltage range 180 - 265 VAC
Inverter voltage 230 VAC
Stand-alone / parallel / 3-phase stand-alone
Search mode off
Ground relay on
Charger on/ off on
Battery charge curve four-stage adaptive with BatterySafe mode
Charge current 75% of the maximum charge current
Victron Gel Deep Discharge (also suitable for Victron AGM Deep Discharge)
Automatic equalisation charging off
Absorption voltage 14.4 / 28.8v
Absorption time up to 8 hours (depending on bulk time)
Float voltage 13.8 / 27.6V
Storage voltage 13.2 / 26.4V (not adjustable)
Repeated absorption time 1 hour
Absorption repeat interval 7 days
Bulk protection on
AC input current limit 12A (= adjustable current limit for PowerControl and PowerAssist functions)
UPS feature on
Dynamic current limiter off
WeakAC off
BoostFactor 2
PowerAssist on
Programmable relay alarm function